It is increasingly important to be able to offer users of a communication network an appropriate quality of service, while allowing mobility during a communication.
To this end, the IEEE (for Institute of Electrical and Electronics Engineers) Committee, and more particularly the entity IEEE 802.21, is proposing a communication network adapted to manage automatic transfer of communications from one subnetwork to another subnetwork of the heterogeneous network in question, regardless of the media used. Such management is referred to as ‘Media Independent Handover (MIH)’.
A MIH function can manage, for a communication that is already set up, a transfer from a subnetwork functioning according to a first access technology (layer 2 of the OSI model) to a subnetwork functioning according to another access technology, in order to offer a mobility for the user within a heterogeneous network.
Therefore, a terminal having an IP (‘Internet Protocol’) session set up for example via a network access point of the Wi-Fi type may be forced to be transferred to a network access point of the GSM (for ‘Global System for Mobile Communication’) type, either because the terminal is moving and the Wi-Fi access point is no longer adapted to the new location of the terminal (i.e. the terminal is leaving the area of coverage of the WiFi access point), or even because the initial communication of the Wi-Fi type encounters transmission problems (i.e. the quality of service can no longer be assured).
This MIH function is more particularly positioned between a level 2 layer, according to the OSI (for Open Systems Interconnection) model, of the protocol stack for wireless communication and a level 3 layer according to the OSI model, of the IP communication protocol stack. It can therefore correspond to a level 2.5 layer located between the network layer and the data link layer of the OSI model.
In particular, it is stipulated that the MIH function should be capable of communicating with different protocols of the IP type, such as ‘SIP’ (for ‘Session Initiation Protocol’) for signalling, such as ‘Mobile IP’ for managing mobility, or even such as ‘Diffserv’ and ‘IntServ’ for managing the quality of service, or QoS.
However, such a MIH function is designed for connectivities of the client-network type. The result of this is that the transfer of a communication from one subnetwork to another subnetwork is limited by the technology associated with each of the access points of the subnetworks, as well as by the resources which are associated with the subnetworks for each of these access points.
More particularly, in such an architecture, a terminal can have access only to subnetworks of the heterogeneous network for which the access points are likely to provide an access to the terminal, i.e. access points in the area of coverage for which the terminal is located and which moreover offer an access technology compatible with the access capacities of the terminal in question.
Consequently, in such conditions, the use of a heterogeneous network is not always optimal.
This invention will improve the situation, by introducing more flexibility into the transfer of technology during a communication set up in a heterogeneous network and while thus allowing more optimal use of the resources offered in the whole of this network. In these conditions, it is also possible to increase the QoS of a communication.